Water Connection Problem
Submissions: 1465   Accuracy:


  Difficulty: Medium   Marks: 4

Every house in the colony has at most one pipe going into it and at most one pipe going out of it. Tanks and taps are to be installed in a manner such that every house with one outgoing pipe but no incoming pipe gets a tank installed on its roof and every house with only an incoming pipe and no outgoing pipe gets a tap. Find the efficient way for the construction of the network of pipes.

The first line contains an integer T denoting the number of test cases. For each test case, the first line contains two integer n & denoting the number of houses and number of pipes respectively. Next, lines contain 3 integer inputs a, b & d, d denoting the diameter of the pipe from the house a to house b.  

For each test case, the output is the number of pairs of tanks and taps installed i.e followed by n lines that contain three integers: house number of tank, house number of tap and the minimum diameter of pipe between them.  



9 6
7 4 98
5 9 72
4 6 10
2 8 22
9 7 17
3 1 66
2 8 22
3 1 66
5 6 10

Connected components are 3->1, 5->9->7->4->6 and 2->8.
Therefore, our answer is 3 followed by 2 8 22, 3 1 66, 5 6 10.

** For More Input/Output Examples Use 'Expected Output' option **

Contributor: Vanshika
Author: Vanshika_pec

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